Fuse



A. G. sTElNMAYER FUSE Filed Dec.` 1o, 195o .U. D 1 h A rd /2 W, h d #MIU W, y s f c v mitin-.rms if zj v ,ai T w /g M Aug. `23, 1932.

Patented Aug. 23, 1932 UNITED STATES PATENT OFFICE A.LWIN G. STEINMAYER, OF MILWAUKEE, WISCONSIN, ASSIGNOB TO LINE vMATERIAL COMPANY, OF SOUTHIMILWAUKEE', WISCONSIN, A CORPORATION OF DELAWARE FUSE Application led December 10,4930. Serial No. 501,284.

This invention relates to certain new and useful improvements in fuses and refers more particularly to a fuse for use with high tension circuits and low amperages.

'5' Heretofore, it has been customary in both 4the closed type of `-fuse and athe lopen type, known in-the art as an expulsion fuse, to form the fuse element per se of a single piece of fusible metal. In most instances the fuse links, as they are` commonly termed,

were of reduced`cross sectional area for a short section of their length, the size of which depended upon the amperage it was desired to have the fuse carry. This construction, v while satisfactory for fuses havin high amperage ratings, is objectionable amperage service, due to the lack-of mechanical strength of the fuse link portions of reduced cross sectional area which are of zo necessity small.

yIn fuses of the closed type, wherein the fuse link is submersed in a liquid and is maintained under spring tension so as to increase the gap. between the fuse terminals immediately upon the rupture of the fuse element, the mechanical weakness of the fuse element is exceptionally objectionable, as the tension :of the spring places considerable strain on the fuse element.

It is, therefore, an object of this invention to provide a fuse of the character described Vwhich will rupture at the desired low amperage and at the same time has considerable mechanical strength.

Another object of this invention Iis to facilitate re-fusing in the field.

And a more specific object of this invention resides in the provision of a tubular casing for the fuse element per se which receives and carries the mechanical strains imposed on the element and which is destroyed upon rupture of the fuse.

With the above and other objects in view vwhich will appear as the description proceeds, 'my invention resides in thevnovel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes 50 in the precise embodiment of the hereindisor low the caps in any suitable manner.

closed invention may be made as come within' the scope of the claims.

In the accompanying drawing, I have illustrated two complete examples of the physical embodiments of my invention constructed according to the best modes I have so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a transverse sectional view taken through a fuse of the closed type illustrating my invention applied thereto;

Figure 2 is a view partly in section and partly in elevation of a conventional expulsion fuse illustrating the application of my invention thereto, and e Figure 3 is a view similar to Figure 1 illustrating still another modification of my invention.

Referring now more particularly to the accompanying drawing, and especially to Figure 1, the numeral 5 represents a fuse tube or cartridge preferably formed of glass or similar material, and to the ends of which contacts or terminals 6 and 7 are secured in any suitable manner. The contact 7 is provided withan axially threaded recess 8 communicating with the interior of the' tube to receive a longitudinally bored screw member 9 which serves to connect, mechanically and-electrically, one end of a flexible conductor 11 with the contact 7.

One end of the flexible conductor 11 is passed through the bore 10 ofA the screw member to be folded upon itself, as at 12, and impinged between the bottom of the threaded recess 8 and the lower face of the screw member to provide a good electrical connection between thefuse contact or terminal and the flexible conductor. The other end of the flexible conductor 11 extends upwardly through the tube 5 and is electrically conneeted with the lower end of a fuse element, indicated generally by the numeral 13. v

The fuse element 18 consists of a link of fusible metal 14 disposed longitudinally within a fiber or glass tube 15 to the ends of which metal caps 16 are secured, the ends of the link 14 being electrically connected with The connection between the fuse element and the flexible conductor 11 is accomplished throu h the medium of a. connector 17 having t e adjacent end of the flexibleI conductor sescrew 19 threaded in the connector 17 secures the cap 16 in the cup shaped recess of the connector.

The upper cap 16 of the fuse element extends into a cup shaped recess 2O formed in a downwardly extended central boss of a cap Amember 21 in which it is secured by a set screw 22 or the like. The cap member 21 is substantially in the shape of an inverted truncated cone and is received in a correspondingly tapered bore 23 in the contact or terminal 6 to thus electrically connect the adjacent end of the fuse element with the contact 6, so that the contacts 6 and 7 are bridged through the fuse element and the flexible conductor 11.

To lmaintain the cap member 21 seated in its bore 23 and to' insure the immediate provision of a large gap between the contacts or terminals of the fuse upon the occurrence of an overload condition in the circuit in which the fuse is connected, a contractile spring 24 is provided, one end of the spring being attached to the connector 17 and the other end to the screw member 9, to at all times subject the fuse element to tension. Heretofore, the tension of the spring was imposed directly on the fuse link, and where the link had of necessity a small cross sectional area, its consequent lack of mechanical strength often was a. source of trouble.

The present invention entirely overcomes this objectionable feature of fuses heretofore in use by the provision of the tubular enclosure 15 which receives and carries the stress imposed on the fuse element by the spring 24 and thus relieves the fuse link of all mechanical strain. Upon rupture of the fuse the relatively thin walls of the tubular enclosure 15 are destroyed by the resulting explosion, so that the spring 24 is immediately freed to create a large gap between the terminals of the fuse. The cap member 21 of course is also blown from its seat in the bore 23 of the upper'fuse contact or terminal so that the gases incidental to the fuse rupture are conveniently vented from the tube 5 to prevent its destruction.

It will be noted that the tubular enclosure 15 not only provides mechanical strength for the fuse element` but serves to confine the arc incidental to the initial rupture, and-to further insure quick extinguishment of the arc, the entire tube 5 is preferably filled with a suitable Huid having a high degree of dielectric strength.

If desired, fuse elements such as described may also be employed in conventional expulsion type fuses and in Figure 2 a typical installation is illustrated. In expulsion fuses, the main supporting tube 5 is open at The member 28 corresponds to the down-- wardly extending central projection of the cap member 21 in the modi cation of Figure 1 and is similarly provided with a cup shaped recess 20 to receive one cap member 16 of the fuse element 13. The opposite cap member 16 of the fuse element 1s secured in a connector 17 similar to the connector 17, but instead of the flexible connecting cable 11, a conductor 29 preferably of soft ielding metal is employed. The upper en of the conductor is secured to the connector 17 and the lower end thereof passes outwardly through the lower end of the tube 5 to be directed upwardly along its exterior and electrically connected with the fuse contact or terminal 7 ina conventional" manner.

The contacts 6 and 7 are thus electrically connected through the conductor 29 and the fuse link 14 and as in the embodiment illustrated in Figure 1, the tubular enclosure 15 of the fuse element provides mechanical strength for an otherwise weak fuse strueture without in any Way interfering with the proper functioning of the fuse.

In some cases it may be desirable to do without the dielectric fluid in the fuse shown in Figure 1 and Figure 3 illustrates another modified form of this invention wherein rapid extinguishment of the arc is insured without the use of a dielectric fluid filling the entire fuse tube. In this construction, the small tube 15 in which the fuse element per se 14 is mounted, isfilled with a fluid having a high degree of dielectric strength. In all other respects the structure of Figure 3 is identical with that illustrated in-Fig-l ure 1.

It is noted that in each of the three modifications illustrated, re-fusing in the field is not only possible but lpractical and from the foregoing description `taken in connection with'the accompanying drawing, it will be readily apparent to those skilled in the art to which an invention of the character described appertains, that I provide a fuse structure which is particularly adapted for use with low amperages, in which the existing objection to fuses maintained under tension by a spring is eliminated, and in which the mechanical strength of the fuse element per seis considerably increased without in an?7 way affecting its proper functioning as a use or its amperage rating.

What I claim as my invention is: 1. In a fuse of the character described, a tube, a first contact member at one end of the tube, a second contact member at vthe other end of the tube, said second contact' member having a tapered bore with its largest diameter outermost, a plug havin 10 a correspondingly tapered outer wall seate in'said opening and having a recess in its inner end portion, a fuse element within the tube, said fuse element having an enclosing casing formed of frangible material and tera minals at the ends of said enclosing casing,

means to readily detachably secure one fuse terminal in the recess of said plug, a connecting member having a recess to receive the other fuse terminal, means providing a positive electrical connection between said connecting member and the iirst mentioned contact member, and a contractile` spring having one end attached to the connecting member and its other end connected with said irstmentioned contact member to maintain a tension on the fuse.

2. In a fuse of the character described, a: housing, a contact member forming a closure for one end thereof and a contact member 2a forming a closure member for the other end thereof, 'said last named contact' member having A a frustro-conical aperture therethrough, a frusto-conical member seated in said aperture having a recess in the inner end thereof, a fuse element having an enclosing casing formed of frangible material and a terminal fitting in said recess, means to clamp said fuse element terminal in said recess, and means electrically connecting the 4,3 other terminal of said fuse element with said first contact member. v

In testimony whereof I have hereunto aiflxed my signature.

ALWIN G. STEINMAYER. 

